Why is it problematic to draw cause-and-effect conclusions based on correlative data?

We cannot draw cause-and-effect conclusions about correlative data because one factor can be related to another factor without causing it.

What does it mean if a researcher claims that a particular result is statistically significant?

If a result is statistically significant, it is probably not due to chance.

Variables:

the events, characteristics, behaviors, or conditions that researchers measure and study.

Subject or participant:

an individual person or animal a researcher studies.

Sample:

a collection of subjects researchers study. Researchers use samples because they cannot study the entire population.

Population:

the collection of people or animals from which researchers draw a sample. Researchers study the sample and generalize their results to the population.

Psychological research, like research in other fields, must meet certain criteria in order to be considered scientific. Research must be:

Research is replicable when others can repeat it and get the same results. When psychologists report what they have found through their research, they also describe in detail how they made their discoveries. This way, other psychologists can repeat the research to see if they can replicate the findings.

After psychologists do their research and make sure it’s replicable, they develop a theory and translate the theory into a precise hypothesis. A hypothesis is a testable prediction of what will happen given a certain set of conditions. Psychologists test a hypothesis by using a specific research method, such as naturalistic observation, a case study, a survey, or an experiment. If the test does not confirm the hypothesis, the psychologist revises or rejects the original theory.

Research Must Be Falsifiable

A good theory or hypothesis also must be falsifiable, which means that it must be stated in a way that makes it possible to reject it. In other words, we have to be able to prove a theory or hypothesis wrong. Theories and hypotheses need to be falsifiable because all researchers can succumb to the confirmation bias. Researchers who display confirmation bias look for and accept evidence that supports what they want to believe and ignore or reject evidence that refutes their beliefs.

Example: Some people theorize that the Loch Ness Monster not only exists but has become intelligent enough to elude detection by hiding in undiscovered, undetectable, underwater caves. This theory is not falsifiable. Researchers can never find these undiscovered caves or the monster that supposedly hides in them, and they have no way to prove this theory wrong.

Research Must Be Precise

By stating hypotheses precisely, psychologists ensure that they can replicate their own and others’ research. To make hypotheses more precise, psychologists use operational definitions to define the variables they study. Operational definitions state exactly how a variable will be measured.

Example: A psychologist conducts an experiment to find out whether toddlers are happier in warm weather or cool weather. She needs to have an operational definition of happiness so that she can measure precisely how happy the toddlers are. She might operationally define happiness as “the number of smiles per hour.”

Research Must Be Parsimonious

The principle of parsimony, also called Occam’s razor, maintains that researchers should apply the simplest explanation possible to any set of observations. For instance, psychologists try to explain results by using well-accepted theories instead of elaborate new hypotheses. Parsimony prevents psychologists from inventing and pursuing outlandish theories.

Parsimony

Parsimonious means “being thrifty or stingy.” A person who values parsimony will apply the thriftiest or most logically economical explanation for a set of phenomena.

Example: Suppose a student consistently falls asleep in her statistics class. She theorizes that before each class, her statistics professor secretly sprays her seat with a nerve gas that makes her very drowsy. If she had applied the principle of parsimony, she would not have come up with this theory. She can account for her sleepiness with a much simpler and more likely explanation: she finds statistics boring.

A Good Theory

A good theory must do two things: organize many observations in a logical way and allow researchers to come up with clear predictions to check the theory.